High-Sensitivity Delay Cells for Low-Voltage Threshold Detection
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Solution Overview
Problem
Existing threshold voltage detection circuits face challenges in efficiently detecting transistor threshold voltages in varying process conditions, especially at low operation voltages and wide frequency ranges, with conventional methods experiencing operational issues due to reduced signal swing and sensitivity to process variations.
Innovation Solution
A high-sensitivity delay cell and circuit design incorporating reconfigurable pass transistors and a boosting capacitor to increase sensitivity to threshold voltage variations, while reducing area overhead and operating robustly across a wide frequency range, even at low operation voltages, using a digital delay-locked loop scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional threshold voltage detection circuits are used, then the circuit can operate in standard conditions, but the sensitivity to threshold voltage variations is insufficient and the circuit fails to operate robustly at low voltages and wide frequency ranges
Solution Approach 1:
The delay cell incorporates reconfigurable pass transistors that can dynamically adjust their configuration based on operating conditions. The transistors can be switched between different states to optimize the delay characteristic sensitivity to threshold voltage variations while maintaining operational robustness across low voltage and wide frequency ranges
Solution Approach 2:
The circuit changes the delay characteristic parameter by adjusting the configuration of pass transistors and utilizing a boosting capacitor to enhance the voltage swing. This allows the delay cell to maintain high sensitivity to threshold voltage variations while adapting to different operating voltages and frequency conditions
2Use of energy by moving object
If the operation voltage is reduced to save power, then power consumption decreases, but the signal swing is reduced and the circuit sensitivity deteriorates
Solution Approach 1:
A boosting capacitor is introduced as an intermediary element to enhance the voltage swing in the delay cell. The capacitor stores and releases energy to compensate for the reduced signal swing at low operating voltages, thereby maintaining the sensitivity to threshold voltage variations without increasing the overall power consumption of the circuit
3Productivity
If process miniaturization is pursued to increase integration density, then more transistors can be integrated, but the influence of process variation on threshold voltage increases
Solution Approach 1:
The circuit replaces direct electrical measurement methods with a time-domain measurement approach using delay cells. By measuring the delay time which is sensitive to threshold voltage variations, the circuit can detect process variations without being directly affected by the increased variability, thus maintaining reliability while allowing process miniaturization for higher integration density
Data Source
AI summary
A circuit configured to detect a threshold voltage includes a first delay circuit, a second delay circuit and a controller. The first delay circuit has a first sensitivity to threshold voltage of a transistor. The first delay circuit may be configured to generate a first output signal delayed with respect to the input signal by a first delay time that changes depending on the digital control code. The second delay circuit has a second sensitivity that is higher than the first sensitivity. The second delay circuit may be configured to generate a second output signal delayed with respect to the input signal by a second delay time. The controller may compare the first and second output signals and may generate a digital output code corresponding to the digital control code when the first delay time is equal to the second delay time to indicate the threshold voltage of the transistor.